During the period between the end the UN vote on partition and the end of the British mandate, Civil War broke out between Jews and Arabs in Palestine. Most of the battles during this period were won by the Jews.

From the moment the United Nations voted to partition, civil war erupted in Palestine. While the Mandate was not scheduled to end until the following May, the British rarely intervened. During the month of December, many mixed areas exchanged populations and demarcation lines became clear. In the beginning of January, members of the Arab Liberation Army, which was comprised primarily of Palestinians trained by surrounding Arab states, entered the country without British interference. On January 10, they attacked the settlement of Kfar Szold, but were repulsed. Jewish settlements throughout the country were isolated, and major efforts had to be expended in order to resupply them. Even Jerusalem could only be resupplied at great cost. One of the most famous and tragic situations was the effort to send reinforcements to the settlements of Kfar Etzion near Jerusalem, which had been cut off from Jewish forces. A platoon of 35 soldiers was sent by foot to reinforce the Etzion settlements. The force was discovered along the way and ambushed -- all 35 of the soldiers were killed. This force became known as the 'Lam'ed Hay' (35 in Hebrew). By March, the tide of battle seemed to be turning against the Jews. As a result of these military setbacks, the United States began to waver in its support of the partition plan. In early April, the Jews launched their first major offensive, called Operation Nachson. The purpose of the operation was to capture a corridor along the road to Jerusalem, and thus secure this route. The major effort along the road was the fight for Kastel, which the Haganah won after a fierce battle on April 10. During the course of the battle, Abd al-Qadir Husayni, the mufti military leader, was killed. This effectively ended the involvement of the Mufti's forces in the war. In the North, the Arab Liberation army developed a concentrated assault on Mishmar Ha'emeq, which was defeated. The forces in Fawzi al- Kawukji were then forced to withdraw to Jenin. In mid-April, the Haganah launched operation Yiftach, whose goal was the liberation of the upper Galilee. On April 18, the Palmach captured Tiberias. On April 21, as the British withdrew from the city of Haifa proper, concentrating their remaining forces in the port area, a brief battle for the city ensued and was quickly won by the Haganah. By May 10, the Arab parts of Safad were captured, and by May 16, Akko was captured. On May 13, Jaffa was captured.

On the Jerusalem front, the Palmach successfully seized most of the major British installations in Jerusalem. However, on May 14, the Etzion bloc fell to the attackers from the Arab Legion. The period leading up to independence was one of successful consolidation. All of the areas allotted the Jewish State in the Galiliee were firmly under Jewish control, as well as some areas that were to have been part of the Arab State. The coastal plain was secure, as was Jewish Jerusalem. The major areas of concern remained the road to Jerusalem, as well as the many isolated settlements in the south.